Proyecto Vainica: valoración e intervención nutricional e insuficiencia cardiaca

Desde el comienzo del milenio diversos estudios muestran la “paradoja de la obesidad en pacientes con insuficiencia cardiaca”. Existe una epidemiología inversa: la obesidad predispone para desarrollar enfermedades cardiovasculares e insuficiencia cardiaca, pero un índice de masa corporal elevado mejora la supervivencia a dos y cinco años. Esta paradoja se ha extendido con posterioridad, a otras enfermedades de carácter crónico y ha sido un tema controvertido en la comunidad científica. Posteriormente, diversos estudios han ido migrando la orientación, relacionando el pronóstico no con el índice de masa corporal en sí, sino con el estado nutricional y el adelgazamiento no intencionado. De modo que el foco de interés está ahora en el estado nutricional de los pacientes y no en su índice de masa corporal. El peso –y por tanto el índice de masa corporal- es un parámetro cambiante en los pacientes con insuficiencia cardiaca, ya que por la naturaleza de su patología, pueden presentar un volumen hídrico aumentado y son susceptibles a descompensaciones edemo-asciticas. Los episodios de descompensación son habitualmente tratados con diuréticos, con el objetivo de eliminar el exceso de líquido, lo que hace que el peso fluctúe rápidamente, a expensas de la reducción del exceso de volumen hídrico. No existe consenso o marcador universalmente aceptado para definir la malnutrición. Por ello, coexisten múltiples métodos de cribado y valoración nutricional. No destacándose ninguno como “gold estándar”..

Kinetic Pathway of the Cylinder-to-Sphere Transition in Block Copolymer Micelles Observed in Situ by Time-Resolved Neutron and Synchrotron Scattering

Here we present an in situ study of the nonequilibrium cylinder-to-sphere morphological transition kinetics on the millisecond range in a model block copolymer micelle system revealing the underlying mechanism and pathways of the process. By employing the stopped-flow mixing technique, the system was rapidly brought (≈100 μs) deep into the instability region, and the kinetics was followed on the time scale of milliseconds using both time-resolved small-angle neutron and X-ray scattering (TR-SANS and TR-SAXS, respectively). Due to the difference in contrast and resolution, SAXS and SANS provide unique complementary information. Our analysis shows that the morphological transition is characterized by a single rate constant indicating a two-state model where the transition proceeds through direct decomposition (fragmentation) of the cylinders without any transient intermediate structures. The cylindrical segments formed in the disintegration process subsequently grow into spherical micelles possibly through the molecular exchange mechanism until near equilibrium micelles are formed. The observation of a two-step kinetic mechanism, fluctuation-induced fragmentation and ″ripening″ processes, provides unique insight into the nonequilibrium behavior of block copolymer micelles in dilute solutions

End-to-End Vector Dynamics of Nonentangled Polymers in Lamellar Block Copolymer Melts: The Role of Junction Point Motion

By using dielectric spectroscopy, we investigate the chain dynamics of nonentangled polyisoprene (PI) under soft confinement in lamellar domains of block copolymer melts with polydimethylsiloxane (PDMS). The data show a dramatic difference in the end-to-end vector dynamics of the PI blocks as compared not only with that of the corresponding homopolymer PI chains but also with respect to previous results for the same blocks under soft confinement in cylindrical domains. Two contributions to the dielectric normal mode relaxation are detected. The data are analyzed by means of a model including contributions from internal chain modes (accounting for the fastest component) and a slow component attributed to the junction point dynamics. The contribution of the internal chain modes is modeled according to the analysis of the Rouse modes obtained from simulations of a generic bead–spring model for strongly segregated symmetric diblock copolymers. In this way it is shown that the internal chain modes of the blocks have time scales close to those expected from the homopolymer chain independently of the structural details. In contrast, the contribution attributed to the junction point dynamics depends critically on minor structural differences. We interpret these findings as a result of the presence of fast moving defects and/or grain boundaries in the lamellar structures formed by these relatively short, nonentangled diblock copolymers